The third sacral dorsal root ganglia are swellings located on the third sacral dorsal roots, proximal to where the dorsal roots join with the third sacral ventral roots.  They are situated in the sacral canal, immediately lateral to the perforation of the dura by the dorsal roots.

The dorsal root ganglia are formed by the cell bodies of somatic and visceral afferent neurons.  Each neuron has a single short axon, which divides into a medial branch, which enters the spinal cord via the dorsal root, and a lateral branch, which passes peripherally to a sensory end organ.